In electronic devices with integrated circuits (ICs), the ICs are typically mounted onto circuit boards. In order to electrically couple connections between the circuit board and the IC, the IC is typically “packaged.” The IC packaging usually provides a small encasement for physically protecting the IC and provides contact pads for coupling to the circuit board. In some applications, the packaged IC may be coupled to the circuit board via bond wires or solder bumps.
One approach to IC packaging comprises a quad-flat no-leads (QFN) package. The QFN package may provide some advantages, such as reduced lead inductance, a near chip scale footprint, thin profile, and low weight. Also, the QFN package typically includes perimeter I/O pads to ease circuit board trace routing, and the exposed copper die-pad technology offers enhanced thermal and electrical performance. QFN packaging may be well suited for applications where size, weight, and thermal and electrical performance are important.
Referring initially to FIGS. 1A-1B, a typical QFN packaged electronic device 90 is now described. The electronic device 90 includes a lead frame 93, an IC 92 on the lead frame, an adhesive layer 96 between the lead frame and the IC, and encapsulation material 91 surrounding the IC and the lead frame. From FIG. 1A to FIG. 1B, a bottom layer of the lead frame 93 is removed to define contacts for the IC 92. A potential drawback to this approach is that the anchoring of the lead frame 93 to the encapsulation material 91 may not be sufficient.
Referring now to FIGS. 2A-2B, a typical QFN/dual-flat no-leads (DFN) packaged electronic device 70 is now described. The electronic device 70 includes a lead frame 75, an IC 72 on the lead frame, an adhesive layer 76 between the lead frame and the IC, an adhesive tape layer 74 carrying the lead frame, and encapsulation material 71 surrounding the IC and the lead frame. From FIG. 2A to FIG. 2B, the adhesive tape layer 74 is removed to define contacts for the IC 72. A potential drawback to this approach is that the adhesive residue from the adhesive tape layer 74 remains on the contacts. Also, there may be mold flash issues from the encapsulation material 71 and lead/pad instability.